Me too. It's just so much quicker to alt-tab to my browser or Telegram or iTunes, even on my beefy rig it takes multiple seconds for my desktop to take control again.

In my experience the vast majority of games that I play don't suffer any perceptible ill effect from running in borderless fullscreen. If you're playing the game competitively it's another story, but for me running around shooting aliens in Destiny 2 or something I haven't noticed any degradation of my experience. There's of course the odd (usually older) game that doesn't support borderless fullscreen, but sometimes there are mods to support it.